lua: Properly support high-range 64 addresses

Lua's native Number type is a 64-bit double with 52-bit precision, which
was causing rounding errors when storing and working with high-range
memory addresses (namely, addresses from the kernel, which are all in
the `0xffffffff........` range).

To work around this, we've made sure to never call `tonumber` on any
variables that represent memory addresses, and instead continue
operating on them with their native types: LuaJIT can work with the
underlying `uint64_t` type for these values and transparently perform
all kinds of numeric operations.

The only limitation of working with native 64-bit types in LuaJIT is
that they cannot be printed with the language's default `string.format`
API. To give better UX to probe writers, these APIs have been
monkeypatched so the `%p` format specifier will now properly handle
64-bit addresses and print them in an appropriate format.

examples/lua/memleak.lua

@@ -148,7 +148,7 @@ return function(BPF, utils)
  if args.pid == nil then
  sym = sym .. " [kernel]"
  end
- return string.format("%s (%x)", sym, addr)
+ return string.format("%s (%p)", sym, addr)
  end
 
  local function print_outstanding()
@@ -174,7 +174,7 @@ return function(BPF, utils)
  end
 
  if args.show_allocs then
- print("\taddr = %x size = %s" % {tonumber(address), tonumber(info.size)})
+ print("\taddr = %p size = %s" % {address, tonumber(info.size)})
  end
  end
  end

examples/lua/offcputime.lua

@@ -107,7 +107,7 @@ return function(BPF, utils)
 
  for k, v in counts:items() do
  for addr in stack_traces:walk(tonumber(k.stack_id)) do
- print(" %-16x %s" % {addr, ksym:lookup(addr)})
+ print(" %-16p %s" % {addr, ksym:lookup(addr)})
  end
  print(" %-16s %s" % {"-", ffi.string(k.name)})
  print(" %d\n" % tonumber(v))

src/lua/bcc/bpf.lua

@@ -188,8 +188,8 @@ function Bpf:attach_uprobe(args)
  local path, addr = LD.check_path_symbol(args.name, args.sym, args.addr)
  local fn = self:load_func(args.fn_name, 'BPF_PROG_TYPE_KPROBE')
  local ptype = args.retprobe and "r" or "p"
- local ev_name = string.format("%s_%s_0x%x", ptype, path:gsub("[^%a%d]", "_"), addr)
- local desc = string.format("%s:uprobes/%s %s:0x%x", ptype, ev_name, path, addr)
+ local ev_name = string.format("%s_%s_0x%p", ptype, path:gsub("[^%a%d]", "_"), addr)
+ local desc = string.format("%s:uprobes/%s %s:0x%p", ptype, ev_name, path, addr)
 
  log.info(desc)
 

src/lua/bcc/ld.lua

@@ -14,6 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ]]
 local ffi = require("ffi")
+local posix = require("bcc.vendor.posix")
 
 local _find_library_cache = {}
 local function _find_library(name)
@@ -60,7 +61,7 @@ local function _find_load_address(path)
  path)
 
  if addr then
- addr = tonumber(addr, 16)
+ addr = posix.tonumber64(addr, 16)
  _find_load_address_cache[path] = addr
  end
 
@@ -85,7 +86,7 @@ local function _find_symbol(path, sym)
  path, sym)
 
  if addr then
- addr = tonumber(addr, 16)
+ addr = posix.tonumber64(addr, 16)
  symbols[sym] = addr
  end
 

src/lua/bcc/sym.lua

@@ -13,6 +13,7 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 ]]
+local posix = require("bcc.vendor.posix")
 local ProcSymbols = class("ProcSymbols")
 
 function ProcSymbols:initialize(pid)
@@ -46,7 +47,7 @@ function ProcSymbols:_get_code_ranges()
  local range = parts[1]:split("-", true)
  assert(#range == 2)
 
- ranges[binary] = {tonumber(range[1], 16), tonumber(range[2], 16)}
+ ranges[binary] = {posix.tonumber64(range[1], 16), posix.tonumber64(range[2], 16)}
  end
  end
 
@@ -83,8 +84,8 @@ function ProcSymbols:_get_sym_ranges(binary)
  for line in proc:lines() do
  local parts = line:split()
  if is_function_sym(parts) then
- local sym_start = tonumber(parts[1], 16)
- local sym_len = tonumber(parts[5], 16)
+ local sym_start = posix.tonumber64(parts[1], 16)
+ local sym_len = posix.tonumber64(parts[5], 16)
  local sym_name = parts[6]
  sym_ranges[sym_name] = {sym_start, sym_len}
  end
@@ -102,10 +103,10 @@ function ProcSymbols:_decode_sym(binary, offset)
  local start = range[1]
  local length = range[2]
  if offset >= start and offset <= (start + length) then
- return string.format("%s+0x%x", name, offset - start)
+ return string.format("%s+0x%p", name, offset - start)
  end
  end
- return string.format("%x", offset)
+ return string.format("%p", offset)
 end
 
 function ProcSymbols:lookup(addr)
@@ -121,7 +122,7 @@ function ProcSymbols:lookup(addr)
  end
  end
 
- return string.format("%x", addr)
+ return string.format("%p", addr)
 end
 
 local KSymbols = class("KSymbols")
@@ -142,7 +143,7 @@ function KSymbols:_load()
  if not first_line then
  local cols = line:split()
  local name = cols[3]
- local addr = tonumber(cols[1], 16)
+ local addr = posix.tonumber64(cols[1], 16)
  table.insert(self.ksyms, {name, addr})
  self.ksym_names[name] = #self.ksyms
  end
@@ -164,7 +165,7 @@ function KSymbols:lookup(addr, with_offset)
 
  if with_offset then
  local offset = addr - self.ksyms[idx][2]
- return "%s %x" % {self.ksyms[idx][1], offset}
+ return "%s %p" % {self.ksyms[idx][1], offset}
  else
  return self.ksyms[idx][1]
  end

src/lua/bcc/table.lua

@@ -286,7 +286,7 @@ function StackTrace:walk(id)
  return nil
  end
 
- local addr = tonumber(pstack[0].ip[i])
+ local addr = pstack[0].ip[i]
  if addr == 0 then
  return nil
  end

src/lua/bcc/vendor/helpers.lua

@@ -1,3 +1,29 @@
+do
+ local ffi = require("ffi")
+ local ptrtype = ffi.typeof("uint64_t")
+ local strformat = string.format
+ function string.format(format, ...)
+ local args = {...}
+ local match_no = 1
+ local newfmt, count = string.gsub(format, "()%%(.-)(%a)",
+ function(_, mods, t)
+ local n = match_no
+ match_no = match_no + 1
+ if t == 'p' and ffi.istype(ptrtype, args[n]) then
+ local lo = tonumber(args[n] % 4294967296ULL)
+ local hi = tonumber(args[n] / 4294967296ULL)
+ args[n] = (hi == 0) and strformat("%x", lo) or strformat("%x%08x", hi, lo)
+ return "%"..mods.."s"
+ end
+ end)
+ if count == 0 then
+ return strformat(format, ...)
+ else
+ return strformat(newfmt, unpack(args,1,select('#',...)))
+ end
+ end
+end
+
 function string.starts(s, p)
  return string.sub(s, 1, string.len(p)) == p
 end
@@ -66,7 +92,7 @@ function table.bsearch(list, value, mkval)
  return mid
  end
  end
- return nil
+ return low - 1
 end
 
 function table.join(a, b)

src/lua/bcc/vendor/posix.lua

@@ -29,6 +29,8 @@ int clock_nanosleep(clockid_t clock_id, int flags,
  const struct timespec *request, struct timespec *remain);
 
 int get_nprocs(void);
+
+uint64_t strtoull(const char *nptr, char **endptr, int base);
 ]]
 
 local CLOCK = {
@@ -62,9 +64,15 @@ local function cpu_count()
  return tonumber(ffi.C.get_nprocs())
 end
 
+local function tonumber64(n, base)
+ assert(type(n) == "string")
+ return ffi.C.strtoull(n, nil, base or 10)
+end
+
 return {
  time_ns=time_ns,
  sleep=sleep,
  CLOCK=CLOCK,
  cpu_count=cpu_count,
+ tonumber64=tonumber64,
 }